Evolution of residual stress in environmental barrier coatings for ceramic matrix composites

陶瓷基复合材料环境屏障涂层残余应力的演变

• 批准号: 2595659
• 金额: --
• 依托单位: University of Oxford
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2021
• 资助国家: 英国
• 起止时间: 2021 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2595659
• 关键词: Evolution; residual; stress; environmental; barrier

Ceramic matrix composites (CMCs) are exciting new materials for use in gas turbine engines, in which an environmental barrier coating (EBC) is needed to protect the CMCs from water vapour attack. The coating also serves as a thermal barrier coating (TBC). The coating acts to increase the operating lifetime and can also offer higher operating temperature with improved fuel efficiency. Significantly, the environmental barrier coating is a prime reliant coating (unlike a TBC), that must not fail in service, since without it the CMC components would have very limited life in the harsh gas turbine engine operating environments. It is known that one major factor governing the life of an environmental barrier coating is its residual stress state, which results from the quenching process of its manufacture via the thermal spray process and the cooling after spraying. The coating stress state also changes with thermal excursions such as heat-treatment and engine operations. This is because of factors that include the mismatch of coefficients of thermal expansion (CTE), thermal gradients, coating crystallization, phase change and sintering, among others. However, there is little knowledge of how these combine to change the stress state, without which it is not currently possible to predict their evolution, nor the effect on the EBC lifetime. The aim of this project is to develop new understanding and models for the evolution of coating stress with time and temperature. The objectives include new observations of the effects of EBC crystallization, phase change, sintering, and thermal mechanical loading on the stresses within the coating and its integrity. The project will apply novel experimental methodologies to investigate the state of stress and strain at high resolution, including synchrotron X-ray diffraction, synchrotron and laboratory X-ray computed tomography, and micro-scale hole-drilling using focused ion beam milling, analysed by 2D and 3D digital image correlation. The study will mostly use ex situ observations of thermally treated coatings, but in situ studies may be achieved using synchrotron X-rays at UK National Facilities. The results will be interpreted using modelling by the finite element method in simulations that will incorporate thermophysical processes such as creep of the bond coat between the substrate and the EBC. This project falls within the EPSRC Materials engineering - ceramics research area' in the Engineering theme listed on this website https://epsrc.ukri.org/research/ourportfolio/themes/ This is an iCASE project, with the support of Rolls-Royce Plc.

陶瓷基复合材料（CMC）是一种新型燃气涡轮机发动机用材料，在燃气涡轮机中需要一种环境阻隔涂层（EBC）来保护CMC免受水蒸气的侵蚀。该涂层还用作热障涂层（TBC）。该涂层用于增加操作寿命，并且还可以提供更高的操作温度和改进的燃料效率。重要的是，环境屏障涂层是主要依赖涂层（与TBC不同），其在使用中必须不会失效，因为没有它，CMC部件在恶劣的燃气涡轮机发动机操作环境中的寿命将非常有限。已知的是，控制环境屏障涂层的寿命的一个主要因素是其残余应力状态，这是由其制造的淬火过程通过热喷涂过程和喷涂后的冷却产生的。涂层的应力状态也会随着热处理和发动机运行等热偏移而变化。这是因为包括热膨胀系数（CTE）、热梯度、涂层结晶、相变和烧结等不匹配的因素。然而，人们对这些联合收割机如何改变应力状态知之甚少，如果没有这些知识，目前就无法预测它们的演变，也无法预测对EBC寿命的影响。该项目的目的是开发新的理解和模型的涂层应力随时间和温度的演变。目标包括EBC结晶，相变，烧结和热机械载荷对涂层内的应力及其完整性的影响的新观察。该项目将采用新的实验方法，以高分辨率调查应力和应变状态，包括同步加速器X射线衍射、同步加速器和实验室X射线计算机断层扫描，以及使用聚焦离子束铣削进行微尺度钻孔，并通过二维和三维数字图像相关性进行分析。这项研究将主要使用非原位观察热处理涂层，但原位研究可能会实现同步加速器X射线在英国国家设施。结果将使用模拟中的有限元法建模来解释，该模拟将包括热物理过程，例如基材和EBC之间的粘结层的蠕变。该项目福尔斯属于本网站https://epsrc.ukri.org/research/ourportfolio/themes/上列出的工程主题中的EPSRC材料工程-陶瓷研究领域。